The invention relates to slitters for sheet metal or the like.
One of the presently common type of sheet metal slitters or cutters employs a pair of shafts with parallel axes each journalled at spaced axial points. One or more pairs of cutters are placed on the shafts, each comprising a pair of abutting cutter wheels having circular cutting edges and mounted on the respective shafts to cut a workpiece as it passes between the shafts. One of the shafts may be a drive shaft and the other a driven shaft. One of the advantages of cutters of this type is that a pair of cutters may be moved to any axial position to cut the sheet metal into any desired width within the limits of the shaft lengths. Another advantage is that more than one cut may be made at a time on the workpiece by using more than one pair of cutters on the shafts.
One of the problems associated with this type of sheet metal cutter is that substantial separation forces are exerted upon the cutters as the sheet metal passes between them. These forces tend to separate the shafts, thereby preventing clean cutting and exerting large wearing forces on the journals at the end of the shaft. The forces of separation also tend to bend or spring the shafts themseleves. Not only is there a resultant wear, with possibilities of distortion of the material of the cutter, but the accuracy of the cutters is also effected.
A somewhat different type of cutter is described in U.S. Pat. No. 1,098,671 granted June 2, 1914, to Lundy for "Sheet Material Cutter", this type of cutter having a U-shaped holder which supports a pair of journalled cutter wheels. In the Lundy U-shaped holder, a pair of slots extend from each side of the holder so that the material, after being cut by the cutter wheels, may pass substantially without tearing or distortion. Nevertheless, in the Lundy cutter only one cut may be made at a time, and the cutter is manipulated manually.
U.S. Pat. No. 679,566 granted July 30, 1901 to Kling for "Metal-Shearing Machine" describes a cutting machine having a pair of cutters held on a single somewhat U-shaped frame, the cutters being driven and in this case the metal instead of passing through slots, passes along guideways, one of which is rather ramp-like in an effort to avoid the tearing of the separated metal.
U.S. Pat. No. 3,126,780 granted Mar. 31, 1964 to Booth for "Sheet Metal Cutting Machine" involves a single cutter although driven by drive shafts which are journalled at their ends, the cutters being located beyond the journals of the drive shafts.
U.S. Pat. No. 2,084,967 granted June 22, 1937 to Babb for "Mechanism for Cutting Sheet Material" and U.S. Pat. No. 2,208,022, granted July 16, 1940 to Dworchuck et al. for "Machine for Cutting Sheet Metal" describe apparatus with single cutters.
Other patents relate to cutters which involve a pair of shafts journalled at their ends on which are mounted paired cutting wheels suitably positioned to cut the sheet metal passing through the shafts at desired spacings. For example, U.S. Pat. No. 91,512, granted June 22, 1869 to Briggs for "Machine for Shearing Metal" and U.S. Pat. No. 813,071 granted Feb. 20, 1906 to Abbott for "Metal Cutting Machine" illustrate machines of this character. Other patents are U.S. Pat. No. 3,195,388 granted July 20, 1965 to Neidigh for "Portable Machine Tool". In these machines there are no means to support the shafts against the opposing forces which occur upon the cutting of the metal tending to spread the shafts apart other than the journals at the ends of the shafts. U.S. Pat. No. 2,777,521 granted Jan. 15, 1957 to Tanis for "Sheet Slitting" machine and U.S. Pat. No. 1,678,186, granted July 25, 1928 to Hoelzel for "Pattern Cutter" do not deal with the problem of the opposing forces tending to spread the shafts apparently because these are not so great as to create a serious problem. A cutting mechanism is described in U.S. Pat. No. 1,723,660 granted Aug. 6, 1929 to Ross for "Cutting Mechanism" which is related more to the problem of supplying a gripping to the material being cut through the cutters.